[Bug c++/89244] New: __builtin_is_constant_evaluated not documented

[msebor at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89244

            Bug ID: 89244
           Summary: __builtin_is_constant_evaluated not documented
           Product: gcc
           Version: 9.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: msebor at gcc dot gnu.org
  Target Milestone: ---

__builtin_is_constant_evaluated added in r263392 to support
std::is_constant_evaluated() does not appear to be documented.